What is the best way to upload files with ASP.NET MVC 2?

Question

What is the best method for uploading files of variable size (either very large or very small to an ASP.NET MVC 2 application file system)?

This is what I understand so far:

It seems like there are two ways that people handle this. (Let's assume the files may be very large or very small)

(1) Handle the upload in a controller action via Request.Files or HttpPostedFileBase, which seems to have a drawback of taking a long time because ASP.NET loads the files into active memory.

or

(2) intercept the file upload early on with an HttpModule which somehow circumvents the performance issue. (I'm a little cloudy on how this works, but I've been using this post http://darrenjohnstone.net/2008/07/15/aspnet-file-upload-module-version-2-beta-1/ as a reference). The part I'm fuzzy about is at what point ASP.NET loads the submitted files to active memory, and how intercepting this in a module actually changes this behavior.

Since the second option is faster, it seems like the better option. But it seems like an application submitting an upload form will probably have some data associated with the file that needs to be persisted in a database. I don't want to make persistence calls in my HttpHandler or HttpModule, (because then I will have two very similar functionalities occurring in different places : the controller and the http handler).

I guess one work around would be to store the target file location in HttpContext.Items, but is this the best way?

One last concern about this is that I want to render an HttpResponse before the file is finished uploading. So, if there is a big file, I will send the user a view with the value of the upload status, and make AJAX calls to keep the status updated. How do I render a result, while keeping the upload process going? Do I need to make an AsyncHandler or AsyncController? Do I need to manually grab another thread?

Thanks a lot guys. I know this is a lot of questions, and probably reflects a general lack of understanding about something. The funny thing about general lacks of understanding is that people who have them also tend to lack the understanding of what understanding they are lacking...so, if anyone can point me in the right direction on that note as well, I would appreciate it.

Answer 1

If I remember correctly from ASP.NET 2.0 large files are being flushed to disk, so even using HttpPostedFileBase there should not be any memory/performance problems. I am not sure asynccontrollers is an solutions here, asynccontrollers is for long running server processes. For an example off AsyncControllers see http://www.aaronstannard.com/post/2011/01/06/asynchonrous-controllers-ASPNET-mvc.aspx

Answer 2

I use this javascript tool

This is the controller (I double check cause IE has a strange behavior) :

<HttpPost()> _
Function UploadExcelPriceList(ByVal id As String) As System.String

    Dim bResult As Boolean = False
    Dim IsIE As Boolean = False
    Dim sFileName As String = ""

    If (Request.Files Is Nothing) OrElse (Request.Files.Count = 0) Then
        If String.IsNullOrEmpty(Request.Params("qqfile")) Then
            Return ("{success:false, error:'request file is empty'}")
        Else
            sFileName = Request.Params("qqfile").ToString
        End If
    Else
        sFileName = Request.Files(0).FileName
        IsIE = True
    End If

    If String.IsNullOrEmpty(sFileName) Then
        Return ("{success:false, error:'request file is empty'}")
    End If

    Dim DocumentName As String = Id & Path.GetExtension(sFileName)

    If IsIE Then
        Try
            Request.Files(0).SaveAs(Path.Combine(My.Settings.TempFolder, DocumentName))
        Catch ex As Exception
            Return ("{success:false, error:'" & ex.Message & "'}")
        End Try
    Else
        Try
            If (Request.InputStream IsNot Nothing) AndAlso (Request.InputStream.CanRead) AndAlso (Request.InputStream.Length > 0) Then
                Using fileStream As FileStream = New FileStream(Path.Combine(My.Settings.TempFolder, DocumentName), FileMode.Create)
                    Dim FileBytes(Core.Convert.ToInt32(Request.InputStream.Length)) As Byte
                    Dim bytesRead As Int32 = 0
                    bytesRead = Request.InputStream.Read(FileBytes, 0, FileBytes.Length)
                    fileStream.Write(FileBytes, 0, bytesRead)
                    fileStream.Flush()
                    fileStream.Close()
                    bytesRead = Nothing
                End Using
            End If
        Catch ex As Exception
            Return ("{success:false, error:'" & ex.Message & "'}")
        End Try
    End If

    Return ("{success:true, id: '" & Id & "'}")

End Function

I put this HTML in my View:

<div id="PopupExcelUploader" title="Carica Listino Excel">
    <div id="uploaderFile"></div>
</div>

and this is the javascript:

function CreateFileUploader() {
    var uploader = new qq.FileUploader({
        element: $('#uploaderFile')[0],
        template: '<div class="qq-uploader">' +
                              '<div class="qq-upload-drop-area"><span>Drop files here to upload</span></div>' +
                              '<div class="qq-upload-button ui-button ui-widget ui-corner-all ui-button-text-only ui-state-default">Seleziona il Listino Excel</div>' +
                              '<ul class="qq-upload-list"></ul>' +
                              '</div>',
        hoverClass: 'ui-state-hover',
        focusClass: 'ui-state-focus',
        action: UploaderAction,
        allowedExtensions: ['xls', 'xlsx'],
        params: { id: ModelId },
        onSubmit: function(file, ext) {
        },
        onComplete: function(id, fileName, responseJSON) {
            if ((responseJSON.success == null) || (responseJSON.success == 'false')) {
                $.jGrowl("Error!", { theme: 'MessageError', life: 3000 });
            }
            else {
                documentUploaded = true;
                $.jGrowl("Document uploaded successfully!", { theme: 'MessageOk', life: 1800 });
                window.setTimeout(function() {
                    $("#PopupExcelUploader").dialog('close');
                    $("#PriceListDynamicGrid").trigger("reloadGrid");
                }, 3000);
            }
        }
    });
}